c Compare the relative effects of forces of different strengths on an object (e.g., strong wind affects an object differently than a breeze).

d Conduct a simple investigation to show what happens when objects of various weights collide with one another (e.g., marbles, balls).

e Show how these concepts apply to various activities (e.g., batting a ball, kicking a ball, hitting a golf ball with a golf club) in terms of force, motion, speed, direction, and distance (e.g. slow, fast, hit hard, hit soft).

4 Students will understand that objects near Earth are pulled toward Earth by gravity.

1 Demonstrate that gravity is a force.

a Demonstrate that a force is required to overcome gravity.

b Use measurement to demonstrate that heavier objects require more force than lighter ones to overcome gravity.

2 Describe the effects of gravity on the motion of an object.

a Compare how the motion of an object rolling up or down a hill changes with the incline of the hill.

b Observe, record, and compare the effect of gravity on several objects in motion (e.g., a thrown ball and a dropped ball falling to Earth).

c Pose questions about gravity and forces.

5 Students will understand that the sun is the main source of heat and light for things living on Earth. They will also understand that the motion of rubbing objects together may produce heat.

1 Provide evidence showing that the sun is the source of heat and light for Earth.

a Identify and classify mechanical and electrical sources of heat.

c Predict, measure, and graph the temperature changes produced by a variety of mechanical machines and electrical devices while they are operating.

3 Demonstrate that heat may be produced when objects are rubbed against one another.

a Identify several examples of how rubbing one object against another produces heat.

b Compare relative differences in the amount of heat given off or force required to move an object over lubricated/non–lubricated surfaces and smooth/rough surfaces (e.g., waterslide with and without water, hands rubbing together with and without lotion).